We've seen references on the board to TSMGs with rewelded receivers, sometimes for prices not much off of those for uncut weapons.

About three years back I was at the range and had the chance to examine an M14 rifle that had been brought by another shooter.

He admitted that it was a reweld, but said that a great deal of care had been taken in what amounted to remanufacturing. In this process, as I recall, he said that the chopped receiver halves had the edges smoothed and dressed. A jig was then used to keep the receiver halves straight during welding. The welded areas had been remilled and whole receiver heat treated and refinished in dark gray phosphate. There was no trace of a weld that I could find, inside or out. It was a very impressive job and obviously shot very well indeed, as he won his match with it. That rifle was the envy all of us M1A shooters!

I heard last year sometime that the gun had been confiscated, and that the owner had been left with a parts kit sans receiver!

With care, can a receiver actually be rewelded so that its strength approaches that of the original forged, uncut item?

Should we just automatically assume that rewelds are far less desirable than uncut guns?

Is there any way to tell a "good" reweld from a "bad" one, besides the cosmetics of the effort, without specialized testing?

Interests:Full time gunsmith who loves Thompsons, 35+ years experience.

Posted 09 March 2004 - 09:09 AM

The main problem associated with re-welded firearms is that most were poorly done; it is possible to get a good result, but I don’t believe that a reweld will ever be as good as original, although it can certainly be good enough, and last just as long.

The first problem is to identify the base metal of the receiver. This can be problematical as the specifications may be unavailable or several options may have been used. If you don’t know the base metal, it can difficult to match up a compatible filler metal. If the filler is not correct, several problems can arise such as cracking of the joint, discoloration in finishing, or stretching in use. Some base metals used in firearms are not considered readily weldable. Although most can be successfully joined, this might require the use of a dissimilar, specialized filler that will not color well when blued or Parkerized.

The second problem to be addressed is the heat treatment of the original part. The M14/M1 rifles are good examples to consider. While there may have been changes throughout production, if I recall correctly, the base metal specified for most was 8620; a carburizing alloy. In heat treatment, the part is raised to a high temperature and subjected to a bath of carbon laden material. The carbon is absorbed by the outer surface of the steel and changes its composition accordingly. After the proscribed length of time required to soak the carbon into a certain depth (usually .010, called the “case”), the part is quenched in a cooling medium. The core has been hardened to a very tough state while the case (or “skin”) of carbonized material becomes very hard. High strength within, hard and resistant to wear without- a great combination.

If a receiver made as above is cut and re-welded, you can see the difficulties in restoring it 100%. While 8620 is a readily weldable alloy and the work could be done perfectly well, it would be difficult to re-heat treat exactly as before. If subjected to re-carburization, the new metal would not have an opportunity to obtain the depth of penetration before the old would receive to much and cause it to become more brittle. A compromise must be reached with a slightly thicker case on the old and thinner on the new.

The TSMG has been made of several alloys and heat treatments over the years and the difficulties can be readily imagined.

Finally, the question of joint preparation is worth mentioning. This is where the skill of the restorer is of great impotence. I have seen some where the torch cut was simply welded over with a “stick electrode” or gas welded with no particular preparation at all. While some of these can be dressed to look alright from the outside on first view, they will surly be bent; as no care was taken to allow for shrinkage. Upon closer inspection of the inside the eye beholds a rough mess that indicates most of the cross section has not been joined at all.

It is possible, in my limited opinion, to restore cut firearms well, but I don’t think the value should be in the same area as an un-cut one. Further, if one is considering such a purchase, have the gun inspected by someone literate and experienced in the process involved to insure you are buying a proper job.

Thanks, guys, for the very complete and thoughtful answers. It sounds like what we're saying is:

Q: With care, can a receiver actually be rewelded so that the strength approaches that if the original, uncut item? A: Yes, it can.

Q: Should we just automaticaly assume that rewelds are far less desirable than uncut guns? A: Yes, we probably should.

Q: Is there any way to tell a "good" reweld from a "bad" one, besides the cosmetics of the effort, without specialized testing? A: No, especially in the absence of the knowledge (and reputation) of the individual or company that did the job.

Thanks for the memory jog: the gun had been produced and sold by MKS. I was so impressed with the rewelded M14 that I tried to buy one. There was a website at the time that gave full details of rewelding and production, and I think the guns were about $1,700. I contacted the distributor and was told that production and distribution had ceased because of legal difficulties.